Sacro-iliac Disease 361 



may be peripheral f \ to the knee, on account of the 



obturator n< ctimes giving a twig to the sacro-iliac joint, and to 



the thigh, on account of associations between the nerves of that joint 

 and other branches of the sacral and lumbar plexuses. There is pain 

 on pressing the fronts of the iliac crests together, and defalcation may 

 distress. Abscess from the joint may open on to the back, or 

 into the pelvis, or into the sheath of the psoas, or into the rectum. 



Ligament*. The fifth lumbar vertebra is connected with the 

 sacrum by the ordinary ligaments of the vertebral column, but there 

 is in addition a strong intertransverse ligament which spreads down 

 into the lateral mass of the sacrum. 



The ilio-lumbar ligament widens out from the tip of the last 

 lumbar transverse process along the back of the iliac crest, giving 

 origin to the quadratus lumborum. 



The great sacro ciatic ligament is attached by a broad base to 

 the posterior inferior iliac spine and to the side of the sacrum and 

 coccyx ; as it passes downwards and outwards it gathers up its 

 into a thick band which afterwards spreads along the inner border of 

 -,hial tuberosity, a falciform process being continued up the 

 ischial ramus. A good deal of the ligament is continued into the 

 origin of the hamstring muscles, especially the biceps. The ligament 

 bounds posteriorly the pelvic outlet and the ischio-rectal fossa, giving 

 origin to the glutens maximus, and closing in the lesser sacro-sciatic 

 foramen. 



The tower acro-*clatic ligament spreads from the ischial spine 

 into the side of the sacrum and coccyx, anterior to the attachment of 

 the greater ligament ; it closes in the great sacro-sciatic foramen, and 

 the internal pudic vessels and nerve wind round it 



The rreat acro-datlc foramen transmits the pyriformis, and, 

 above it, the gluteal vessels and the superior gluteal nerve ; below it, 

 the sciatic and internal pudic vessels and nerves, and small branches 

 of the sacral plexus. 



By the mailer foramen the obturator internus and its nerve 

 leave the pelvis, and the internal pudic vessels and nerve re-enter on 

 their way to die ischio-rectal fossa. 



The pubic jrmpbjrsi* is enclosed by anterior, posterior, and 

 superior, and the sub-pubic ligaments. 



Each osseous surface is covered by an oval fibro-cartilaginous 

 plate, and between these plates is an elastic pulp ; as pregnancy ' 

 approaches a synovial membrane may be developed in the joint 



Arterial twigs enter the joint from the obturator and deep epigastric ; 

 filaments of nerve come from the obturator. 



The articulation of the fifth lumbar vertebra with the sacrum forms 

 the Mero-Tertebral angle, which may be felt by a long finger in the 

 rectum. It most not be taken for a stricture of the bowel, nor for a 



